Thermal evolution process, properties and photocatalytic activity of sol-gel derived nanocrystalline anatase in dye degradation process

Abstract

Nanocrystalline anatase aimed to be used as a photocatalyst for dye degradation processes in industrial effluents and has been prepared and investigated. Amorphous titania gel has been prepared using sol–gel process by slow hydrolysis of titanium n–butoxide. The prepared gel has been investigated using Fourier–Transformed Infra–Red Spectroscopy (FTIR), Powder X–ray Diffraction (PXRD), Differential Thermal Analysis (DTA), Thermo–Gravimetric Analysis (TGA), N2 gas adsorption–desorption isotherms and Diffuse Reflectance UV–Vis Spectroscopy (DRS). It was determined that the amorphous gel was comprised of non-hydrolyzed butoxy groups as well as hydroxyl groups bonded to titanium. The thermal evolution of gel is consisted of five steps: elimination of adsorbed water and butanol in temperature range between room temperature and 200 °C, decomposition and elimination of butoxy groups between 200 and 300°C. The crystallization of anatase centered at 404°C, transformation to rutile starting from 540 °C and oxidation of char and tar above 600°C. Thermal treatment of gel at 350 °C for 2 h yields with pure nanocrystalline anatase with average crystallite size of 13.2±0.2 nm, specific surface area of 65.48 m2g–1 and bandgap, of 3.24 eV. The preliminary assessment of prepared catalyst photocatalytic activity was obtained through degradation process of methylene blue dye under UV light and the 99 % degradation of dye took place within 150 min.